The present invention relates to a method for fusion splicing optical fibers using heat generated by a gas discharge between electrodes.
The optical fiber fusion splicing method employing gas discharge is disclosed, for example, in U.S. Pat. No. 3,960,531 "Method and apparatus for splicing optical fibers" issued June 1, 1976 and has been put to practical use. In the conventional fusion splicing method employing a gas discharge, optical fibers which are to be spliced are aligned end-to-end, and a pair of spaced electrodes are energized to generate an electrical field at the junction between the fibers which is of sufficient magnitude to create a gas discharge or electric arc that melts the ends of the fibers and fuses or splices them together. The power applied across the electrodes is a DC current or an AC current of the commercial power source frequency. For producing a gas discharge, a high voltage, for example, of 3 to 6 KV must be applied across electrodes which are spaced, for example, 1.5 mm apart and, when the discharge starts to effect a flow of current, the voltage between the electrodes drops to a discharge sustain voltage Vg. With the prior art method, a high AC voltage Vsi necessary for starting the discharge is always supplied to the electrodes, and during the discharge the difference voltage between the voltage Vsi and the sustain voltage Vg is produced across a stabilizing resistor connected in series with the discharge electrodes. Accordingly, the conventional method requires a high-voltage transformer for generating the high voltage Vsi at all times and this transformer is bulky and heavy. The power determined by the product of the abovesaid difference voltage, Vsi-Vg, and the discharge current is dissipated by the abovementioned stabilizing resistor and this power is not used for the fusion splice and hence it is wasteful. Since this wasteful power is large, the high-voltage transformer must have a large capacity and consequently the transformer is inevitably bulky and heavy. Further, such useless power dissipation is undesirable especially when the fusion splicing machine operates from a battery. For splicing optical fibers in places which exhibit difficult work conditions, such as a narrow manhole or hand hole and a telephone pole, a splicing machine operating from a small, lightweight battery is desired. With the prior art fusion splicing method, however, it is difficult to realize such a machine.
Heretofore it has been proposed to make the transformer small and lightweight by raising the frequency of the AC voltage, for example, up to between 16 and 60 KHz. In this method, however, the AC voltage of the high frequency is used as the high voltage Vsi for starting the discharge and the AC voltage is supplied to the discharge electrodes at all times, so that much power is wasted by the stabilizing resistor as described above. Accordingly, this method does not provide improvement in power saving.